Do not use dangerous default argument [].

Default arguments get evaluated only once when the function is defined, and
are then shared across all instances of the function. If the argument is then
mutated, this can cause hard to find bugs. See
https://docs.python.org/3/tutorial/controlflow.html#default-argument-values

* gn3/authentication.py (create_group): Do not use [] as the default argument.

1 files changed, 6 insertions, 2 deletions

diff --git a/gn3/authentication.py b/gn3/authentication.py
index 6719631..1ccffcc 100644
--- a/gn3/authentication.py
+++ b/gn3/authentication.py
@@ -145,9 +145,13 @@ def get_user_info_by_key(key: str, value: str,
 
 
 def create_group(conn: Redis, group_name: Optional[str],
-                 admin_user_uids: List = [],
-                 member_user_uids: List = []) -> Optional[Dict]:
+                 admin_user_uids: List = None,
+                 member_user_uids: List = None) -> Optional[Dict]:
     """Create a group given the group name, members and admins of that group."""
+    if admin_user_uids is None:
+        admin_user_uids = []
+    if member_user_uids is None:
+        member_user_uids = []
     if group_name and bool(admin_user_uids + member_user_uids):
         timestamp = datetime.datetime.utcnow().strftime('%b %d %Y %I:%M%p')
         group = {